Heretofore, paired conveyors for seizing and conveying a glass plate have comprised a combination of a support conveyor for supporting the glass plate in a defined state and a press conveyor for pressing and holding the glass plate against the support conveyor.
The press conveyor has a width narrower than that of the support conveyor and the lower end of the press conveyor is situated above the lower edge of the glass plate to be conveyed, the press conveyor being so constructed that the glass plate is resiliently pressed toward the support conveyor.
A plurality of grinding wheels are disposed in series below the press conveyor.
On the other hand, the support conveyor is extended near the lower edge of the glass plate so as to support the glass plate put under a grinding load over a range as wide as possible.
That is, the support conveyor is situated on the side of the glass plate opposite to the side where the grinding wheel is disposed. The lower end of the support conveyor is situated below the lower end of the press conveyor and above the lower edge of the glass plate.
The glass plate is seized between the press conveyor and the support conveyor. At a stepped portion formed between the lower end of the press conveyor and the lower end of the support conveyor, the glass plate is disposed such that it is supported on one side thereof by the support conveyor and exposed on the other side thereof to the press conveyor with the lower edge being exposed downwardly. The exposed side and the lower edge of the glass plate are chamfered or ground by the grinding wheels.
The structure of the conveyor may generally be classified into two types, that is, a caterpillar conveyor type in which rectangular holding members are attached to an endless chain and a conventional belt conveyor type.
The conveyor system according to this invention includes such a system where the caterpillar conveyor is employed for both the press conveyor and the support conveyor and such a combination system in which the caterpillar conveyor is used for the press conveyor and the belt conveyor is used for the support conveyor.
However, the size of a glass plate capable of being subject to chamfering or edge grinding is restricted by the distance of the step portion between the press conveyor and the support conveyor in the conventional glass plate grinding apparatus having the foregoing structure. That is, a glass plate of a size smaller than the distance of the step cannot be held between the conveyors. Further, even if a glass plate has a size a little larger than the distance of the step, it cannot be held firmly between the conveyors but rather is readily displaced during grinding work, by which the grinding of the glass plate in such size cannot be effected.
Thus, a grinding apparatus adapted to perform grinding or beveling for a glass plate of a larger width cannot be applied to grinding or beveling for a smaller size glass plate.
On the other hand, in a grinding apparatus in which the step is reduced for the purpose of beveling and grinding a smaller size glass plate, if a grinding wheel is brought into contact with the glass plate over a wide range (with a smaller angle of contact), for performing beveling over a large width, the wheel will fail to perform the beveling due to contact with the press conveyor.
As a countermeasure, a grinding apparatus in which the support conveyor is made movable vertically relative to the press conveyor has been known.
In the case of performing beveling over a larger width, the support conveyor is lowered to descend the lower pass line of the glass plate so that the area of contact of the grinding wheel with the glass plate is made wider.
In the case of beveling or grinding a smaller size glass plate, the support conveyor is moved upwardly to raise the pass line of the glass plate, and at the same time the step between the press conveyor and the support conveyor is decreased and the glass plate small in size is seized, so that the area of contact of the grinding wheel with the glass plate is decreased for performing beveling over a narrow width.
However, in the grinding apparatus of this type, since the height of the lower pass line of the glass plate varies depending on the vertical movement of the support conveyor, vertical adjustment has been required each time for the glass plate feed conveyor and discharge conveyor connected to the apparatus main body.
Further, variation of the pass line of the glass plate relative to the grinding wheels requires the adjustment of the position of the water feed pipe or the like to the grinding wheels, re-adjustment of the status and position of the grinding wheels which have previously been adjusted and set, and replacement of the grinding wheels due to the change in the grinding position.